The present invention relates generally to infrared photodetectors, and more specifically to a new class of photodetectors which comprise passive structures which reduce self-interference from thermal radiation from the device or its surroundings.
The thermal emissivity of a body characterizes the flux of thermal "blackbody" radiation emitted from the body's surfaces. The ability to passively detect and measure such thermal radiation, e.g., through the use of a photodetector, allows detection and analysis of objects at a distance. Such features as temperature and surface condition can be determined in many cases.
Considerable technological difficulties appear in the use of photodetectors sensitive to thermal radiation characteristic of normal environments (roughly 3 to 30 .mu.m in wavelength). The surfaces of the photodetector and its housing must be cooled well below room temperature, or the thermal radiation emitted by these surfaces will compromise the limiting sensitivity of the photodetector.